An Account of the Aurora Borealis, Seen at London, on the 30th of March Last, as It Was Curiously Observ d by Martin Folkes, Esq; R. S. Soc.

I. An Account of the Aurora Borealis, seen at London, on the 30th of March last, as it was curiously Observ'd by Martin Folkes, Esq; R.S.Soc. Being in the Street, between 8 and 9 a Clock on Saturday last, (30 Martii) I perceiv'd a Light over the Houses to the Northwards, little inferior to that the Full Moon gives when she first rises. Upon this, suspecting some such Meteor as we saw the last Year, I made all the haste I could into the Fields, where I immediately found my Conjecture verified; and was for some time agreeably entertain'd with the sight of an Aurora Borealis, attended with most of the Phenomena that have been describ'd in that very remarkable one of the 6th of March, 1715-6. The whole Northern Part of the Horizon was in the same manner cover'd with somewhat resembling a very considerable Light, whose lower part was pretty well defin'd by the common Edge of the Cloud, but the upper dy'd away more gradually. This upper Limb of the Light resembling the Arch of a Circle, whose highest Point between 9 and 10 of the Clock (when the Meteor was most considerable) was elevated about 12 Degrees, and bore, as I imagin'd about 20 deg. Westward of the due North. It touch'd the Horizon in the West at the distance of about 65 or 70 Degrees from the North, whence the whole intercepted Arc of the Horizon would have been of near 100 Deg. had not some few Degrees in the East been hid by Clouds which lay between us and the Meteor. The seeming black Cloud when I first saw it, ran nearly parallel to the Horizon, and at the distance of 6 or 7 Degrees: but in about half an Hour it changed its Figure very very much, sinking down in the North to about half its height, and rising in the West near as much. What I principally took notice of this for, was that the Light issuing from behind it did not change with it, but remain'd of the same Figure, however the Cloud approached or receded from differing Parts of its Limb. There arose at first some Streams in the N.N.W. but of no considerable Length, few of them passing 5 Degrees above the Arch; but beginning from behind the seeming Cloud, so as to be about 12 Degrees high in all. They were Pointed at the Ends, and nearly vertical to the Horizon. Between times there was nothing but the Arch to be seen, and that only resembling a common Aurora; and again in an instant, by a sort of tremulous Motion, several Parts of it would appear converted into a vast number of parallel Streams, for the most part very little higher than the Arch itself. About 20 Minutes before Ten, a small part of the Arch, almost due North, grew remarkably lighter than the rest, and continued to encrease for about half a Minute; when there suddenly broke out some very tall Streams of at least 60 Degrees high, as I found by one in particular which arose full North, and passing over the Pole star itself, reach'd some Degrees beyond it. This was the most remarkable time of the Appearance, some such Lances, though not so high, immediately shooting out of the Place that first of all radiated, as did some more a good way to the East. They were all nearly Perpendicular to the Horizon, and most of them did arise quite from the black Substance at Bottom, tho' I saw some few that did not reach so low, appearing as if their lower Parts had been broken off. Some of them were full as bright as any I saw the last Year, the Axes (if I may so call them) of some of the tallest Streams coming up very near near to the Colour of that pale Fire we see in some sorts of Lightning. About this time the Ground Westward was all cover'd with an odd sort of Mist, the same from which I remember last Year a great many People said there came an ill smell, which I did not at all perceive; however as I remember it to be the very same Appearance, I thought it might not be improper just to take notice of it. About 10 the Phenomenon very much decreas'd, and so continued till after 11, only sending up now and then 2 or 3 Streams. At half an Hour after 11 it was again pretty much encreas'd, and I saw it again send out some Streams almost as considerable as any I had before seen this Evening; the Arch yet continued, but not so entire; and from what I could judge, its middle was some Degrees nearer the North than when I first took notice of it. Till a quarter of an Hour before 12 the light continually abated, and then I left it; but a Watchman, I order'd to bring me an Account of it next Morning, tells me it continued till towards Day-break, but never stream'd remarkably after I went away. Tho' I could not this time see any Stars through the black Matter at Bottom, I am sensible it was not a Cloud, tho' it bore the resemblance of one: for when a real Cloud (as several small ones did) came over any part of it, their difference was very conspicuous. I have since receiv'd two Letters, one from Wisbech in the Isle of Ely, the other from within 14 Miles of the Bath, both which take notice of it, tho' with no further Particulars, than that on Saturday Night, they had seen the same Light, tho' not so considerable, as in the beginning of March the last Year. H. Gui...